Effect of fly ash on setting times of concrete Comparison of result by using Kosovo’s and Japan’s fly ash

2017 ◽  
Author(s):  
Anjeza Alaj ◽  
Tatsuya Numao
Keyword(s):  
Fly Ash ◽  
Setting Times

Effect of NaOH and Water Contents on Solidification of Sodium Silicate Free Geopolymer

2014 ◽  
Vol 625 ◽  
pp. 3-6 ◽  
Author(s):  
Ahmer Ali Siyal ◽  
Lukman Ismail ◽  
Zakaria Man ◽  
Khairun Azizi Azizli
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Fly Ash ◽  
Portland Cement ◽  
Sodium Hydroxide ◽  
Fourier Transform Infrared Spectroscopy ◽  
Setting Times ◽  
Behavior Study ◽  
Class F Fly Ash ◽  
Water Contents

Geopolymers are fast setting binder materials possessing strength comparable with Portland cement. In this study solidification and bonding behavior of sodium hydroxide activated class F fly ash geopolymers were determined. Solidification was determined using Vicat apparatus and bonding behavior study was carried out using Fourier transform infrared spectroscopy (FTIR). The decrease in solidification time from 105 minutes to 90 minutes was observed when Na/Al ratio increased from 1 to 1.4. By changing liquid to solid (L/S) ratio from 0.154 to 0.231 initial and final setting times found to increase. FTIR results showed main peaks at 1000 cm-1and 1432 cm-1due to asymmetric stretching of Al-O/ Si-O bonds.

scholarly journals Characterization and Performance of Mechanical Properties of GGBS Based Geo Polymer Mortars

2019 ◽  
Vol 8 (4) ◽  
pp. 8336-8342
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Sodium Hydroxide ◽  
Construction Industry ◽  
Research Paper ◽  
Setting Times ◽  
And Performance ◽  
Creep And Shrinkage

From decades it has been recognized that Geopolymer will considerably replace the role of cement in the construction industry. In general, Geopolymer exhibits the property of the peak compressive strength, minimal creep and shrinkage. In this current research paper, Geopolymer mortar is prepared by using GGBS and Fly ash. The mix proportions are of (100-60)%GGBS with Fly ash by 10% replacement. The alkali activators Na0H and Na2Sio3 are used in the study for two different molarities of 4&8. The ratio to Sodium silicates to sodium hydroxide is maintained from 1.5, 2, 2.5 & 3 were used. Mortars are prepared and studied the effect of molarities of alkali activators in their setting times and strengths

scholarly journals Strength and Setting Times of Low Calcium Fly Ash-based Geopolymer Mortar

2008 ◽  
Vol 2 (4) ◽  
Author(s):  
Djwantoro Hardjito ◽  
Chua Chung Cheak ◽  
Carrie Ho Lee Ing
Keyword(s):  
Fly Ash ◽  
Setting Times ◽  
Low Calcium

scholarly journals Effect of Copolymer Latexes on Physicomechanical Properties of Mortar Containing High Volume Fly Ash as a Replacement Material of Cement

2014 ◽  
Vol 2014 ◽  
pp. 1-11
Author(s):  
El-Sayed Negim ◽  
Latipa Kozhamzharova ◽  
Yeligbayeva Gulzhakhan ◽  
Jamal Khatib ◽  
Lyazzat Bekbayeva ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
High Volume ◽  
Physicomechanical Properties ◽  
Partial Replacement ◽  
Setting Times ◽  
High Volume Fly Ash ◽  
Scanning Electron

This paper investigates the physicomechanical properties of mortar containing high volume of fly ash (FA) as partial replacement of cement in presence of copolymer latexes. Portland cement (PC) was partially replaced with 0, 10, 20, 30 50, and 60% FA. Copolymer latexes were used based on 2-hydroxyethyl acrylate (2-HEA) and 2-hydroxymethylacrylate (2-HEMA). Testing included workability, setting time, absorption, chemically combined water content, compressive strength, and scanning electron microscopy (SEM). The addition of FA to mortar as replacement of PC affected the physicomechanical properties of mortar. As the content of FA in the concrete increased, the setting times (initial and final) were elongated. The results obtained at 28 days of curing indicate that the maximum properties of mortar occur at around 30% FA. Beyond 30% FA the properties of mortar reduce and at 60% FA the properties of mortar are lower than those of the reference mortar without FA. However, the addition of polymer latexes into mortar containing FA improved most of the physicomechanical properties of mortar at all curing times. Compressive strength, combined water, and workability of mortar containing FA premixed with latexes are higher than those of mortar containing FA without latexes.

Reducing Set Retardation in High-Volume Fly Ash Mixtures with the Use of Limestone

2012 ◽  
Vol 2290 (1) ◽  
pp. 139-146 ◽  
Author(s):  
Lisa R. Gurney ◽  
Dale P. Bentz ◽  
Taijiro Sato ◽  
W. Jason Weiss
Keyword(s):  
Fly Ash ◽  
Volume Fraction ◽  
High Volume ◽  
Reaction Rates ◽  
Limestone Powder ◽  
Water Volume ◽  
Early Age ◽  
Ternary Blends ◽  
Setting Times ◽  
High Volume Fly Ash

High-volume fly ash (HVFA) concretes are attractive not only because they reduce cement content and the associated greenhouse gases, but also because they avoid landfilling excessive quantities of fly ash. These sustainability benefits are often tempered by practical constructability limitations that may exist for HVFA concretes: retardation and diminution of the early-age reaction, delay in setting (and finishing operations), and lower early-age strength. This paper explores the alleviation of these deficiencies in HVFA mixtures by the incorporation of fine limestone powders into ternary blends. Isothermal calorimetry and Vicat needle penetration measurements are employed to assess reaction rates and setting times, respectively. A systematic variation of the content and fineness of the limestone powder in mixtures containing either a Class C or a Class F fly ash indicates that setting times are linearly correlated with the surface area supplied by the limestone. Comparison of a limestone system to a system containing an inert titanium dioxide of similar particle size indicates that the acceleration and amplification effects of the limestone can be attributed to both physical (nucleation) and chemical (additional calcium ions) processes. The results indicate that ternary blends with 40% of the cement by volume replaced by 30% to 35% fly ash and 5% to 10% limestone at a constant water volume fraction can be achieved without significant delay in setting.

scholarly journals Predictive Model of Setting Times and Compressive Strengths for Low-Alkali, Ambient-Cured, Fly Ash/Slag-Based Geopolymers

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 920 ◽  
Author(s):  
Supphatuch Ukritnukun ◽  
Pramod Koshy ◽  
Aditya Rawal ◽  
Arnaud Castel ◽  
Charles Christopher Sorrell
Keyword(s):  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Setting Time ◽  
Curing Temperature ◽  
Setting Times ◽  
Optimal Mix ◽  
High Alkalinity ◽  
Class F Fly Ash ◽  
Furnace Slag

The effects of curing temperature, blast furnace slag content, and Ms on the initial and final setting times, and compressive strengths of geopolymer paste and mortars are examined. The present work demonstrates that ambient-cured geopolymer pastes and mortars can be fabricated without requiring high alkalinity activators or thermal curing, provided that the ratios of Class F fly ash (40–90 wt%), blast furnace slag (10–60 wt%), and low alkalinity sodium silicate (Ms = 1.5, 1.7, 2.0) are appropriately balanced. Eighteen mix designs were assessed against the criteria for setting time and compressive strength according to ASTM C150 and AS 3972. Using these data, flexible and reproducible mix designs in terms of the fly ash/slag ratio and Ms were mapped and categorised. The optimal mix designs are 30–40 wt% slag with silicate modulus (Ms) = 1.5–1.7. These data were used to generate predictive models for initial and final setting times and for ultimate curing times and ultimate compressive strengths. These projected data indicate that compressive strengths >100 MPa can be achieved after ambient curing for >56 days of mixes of ≥40 wt% slag.

scholarly journals SETTING TIMES OF PORTLAND CEMENT–METAKAOLIN–FLY ASH BLENDS / PORTLANDCEMENČIO, METAKAOLINO IR LAKIŲJŲ PELENŲ MIŠINIŲ RIŠIMOSI TERMINAI

2011 ◽  
Vol 17 (1) ◽  
pp. 55-62 ◽  
Author(s):  
David Snelson ◽  
Stan Wild ◽  
Martin O’Farrell
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Partial Replacement ◽  
Setting Times ◽  
Pozzolanic Materials

In the present study two pozzolanic materials are used, Metakaolin (MK) and Fly Ash (PFA), as binary and ternary partial replacement binders with Portland cement (PC) to investigate their effect on standard consistence and setting times of paste. To maintain standard consistency for MK–PC pastes increasing w/b ratios are required with increasing MK levels, whereas PFA has little influence on consistency. For binary MK–PC pastes there are substantial increases in initial and final setting times at 5% MK followed by decreases at 10 and 15% MK before further increases at 20% MK. For binary PFA–PC pastes however setting times increase at approximately the same rate up to 30% PFA and then increase more sharply between 30% PFA and 40% PFA. In general the effects of both PFA and MK on consistency and setting times in binary pastes are reflected in the behaviour of the ternary pastes although the two pozzolans do not behave completely independently of each other. The different ways in which the two pozzolans influence setting times is explained in terms of differences in their pozzolanic activities and in the manner in which they influence the availability of water for hydration. Santrauka Šiame tyrime naudojamos dvi pucolaninės medžiagos—metakaolinas (MK) ir lakieji pelenai (PFA), kaip dviejų ir trijų komponentų dalinio pakeitimo rišikliai su portlandcemenčiu (PC), siekiant ištirti jų poveikį standartinėms konsistencijoms ir reguliuoti mišinio kietėjimo laiką. Siekiant išlaikyti standartinę MK–PC mišinio konsistenciją, didinant vandens ir rišamųjų medžiagų santykius, reikia didinti MK lygį, nes PFA turi mažai įtakos konsistencijai. Dviejų komponentų MK–PC mišiniams svarbu padidinti pradinius ir galutinius kietėjimo laikus 5% MK, po sumažėjimo 10 ir 15% MK, prieš tolesnį padidinimą 20% MK. Dviejų komponentų PFA–PC mišinių kietėjimo laikui padidinti maždaug tokiomis pačiomis normomis iki 30% PFA ir tuomet didinti atsargiau tarp 30% PFA ir 40% PFA. Apskritai PFA ir MK poveikis konsistencijai ir kietėjimo laikui abiejuose mišiniuose matomas iš trijų mišinio komponentų elgsenos, nors du pucolanai nėra visiškai nepriklausomi vienas nuo kito. Kiti būdai, kuriais du pucolanai daro įtaką kietėjimo laikui, yra pristatyti kalbant apie jų pucolaninės veiklos skirtumus ir jų elgseną, kurios metu jie daro įtaką vandens galimybei hidratuotis.

Effect of Fly Ash and nanoCaCO3 on the Setting Time of Cement Paste

2013 ◽  
Vol 405-408 ◽  
pp. 2885-2888
Author(s):  
Zhi Qin Zhao ◽  
Zhi Ge ◽  
Ren Juan Sun ◽  
Gong Feng Xin ◽  
Da Wei Huang
Keyword(s):  
Experimental Study ◽  
Fly Ash ◽  
Cement Paste ◽  
Setting Time ◽  
Test Group ◽  
Cementitious Materials ◽  
Ash Content ◽  
Setting Times

This paper presents an experimental study to evaluate the effects of fly ash and nanoCaCO3 on setting time of cement paste. The test group included the contents of fly ash was 30%, 40%, 50%, 60% and content of nanoCaCO3 was 2.5%, 5%, 10%, 20%. Results indicate that setting time was increased with the incorporation of fly ash, shortened with the incorporation of nanoCaCO3. The incorporation of 5% nanoCaCO3 by mass of cementitious materials reduced initial and final setting times by 60 and 70 min, respectively. In comparison to the referenced paste with 40% fly ash. The best fly ash content appear to be 40% when nanoCaCO3 was added.

scholarly journals Investigation on the Compressive Strength and Time of Setting of Low-Calcium Fly Ash Geopolymer Paste Using Response Surface Methodology

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3461
Author(s):  
Pauline Rose J. Quiatchon ◽  
Ithan Jessemar Rebato Dollente ◽  
Anabel Balderama Abulencia ◽  
Roneh Glenn De Guzman Libre ◽  
Ma. Beatrice Diño Villoria ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Unconfined Compressive Strength ◽  
Setting Time ◽  
Initial Setting Time ◽  
Alkali Activator ◽  
Setting Times ◽  
Confirmatory Tests ◽  
Initial Setting

Approximately 2.78 Mt of coal fly ash is produced in the Philippines, with a low utilization rate. Using fly ash-based geopolymer for construction will lessen the load sent to landfills and will result in lower GHG emissions compared to OPC. It is necessary to characterize the fly ash and optimize the geopolymer components to determine if it can replace OPC for in situ applications. The activator-to-precursor ratio, the water-to-solids ratio, and the sodium hydroxide-to-sodium silicate ratio were optimized using a randomized I-optimal design from the experimental results of 21 runs with five replicates, for a total of 105 specimens of 50 mm × 50 mm × 50 mm paste cubes. The engineering properties chosen as the optimization responses were the unconfined compressive strength (UCS), the initial setting time, and the final setting time. The samples were also ambient-cured with the outdoor temperature ranging from 30 °C to 35 °C and relative humidity of 50% ± 10% to simulate the on-site environment. Runs with high unconfined compressive strength (UCS) and short setting times were observed to have a low water-to-solids (W/S) ratio. All runs with a UCS greater than 20 MPa had a W/S ratio of 0.2, and the runs with the lowest UCS had a W/S of 0.4. The initial setting time for design mixes with a W/S ratio of 0.2 ranged from 8 to 105 min. Meanwhile, five out of seven design mixes with a W/S ratio of 0.4 took longer than 1440 min to set. Specimens with an alkali activator ratio (NaOH/WG) of 0.5 (1:2) and 0.4 (1:2.5) also had significantly lower setting times than those with an alkali activator ratio of 1. The RSM model was verified through confirmatory tests. The results of the confirmatory tests are agreeable, with deviations from the expected UCS ranging from 0 to 38.12%. The generated model is a reliable reference to estimate the UCS and setting time of low-calcium FA geopolymer paste for in situ applications.

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